Seedlings: success and failure

ant damp off

Spring must be here because I have started seed sowing. It is always hard to hold off the first sowing because there is nothing nicer, on a cold day, to peer into the propagator and see the fresh signs of growth and all that potential as the tiny green shoots push through the soil (or, more often in my case, the white dusting of perlite.

If you are sowing on the windowsill it is not a good idea to sow too early because you have to consider the poor light levels and where you will grow-on your seedlings before you can put them outside. Luckily I have a big propagator in the greenhouse and although the greenhouse is (largely) not heated, it is frost free and I have plenty of room. So sowing started two weeks ago and things are up!

But there are problems already. The disadvantage of sowing early is that you want to maintain all the expensive heat you are paying for and the stuffy, moist, warm conditions can be just as suitable for damping off as for the seedlings.

Damping off is caused by pythium or phytophthera fungi which attack the seedlings at ground level. The white mycelium can be seen growing across the compost surface and, typically, the seedlings fall over and shrivel. You can see this on the photo of my antirrhinum seedlings above. Antirrhinums are very prone to this disease but almost any seedlings can be affected.

You can help avoid the problem if you:

1. Use clean or new trays

2. Use fresh compost

3. Sow thinly

4. Use mains water rather than rainwater

5. Ventilate the seedlings to avoid stuffy conditions

I did all these although the seeds were sown a bit thickly. I did ventilate well when the seedlings appeared but On Sunday, because it was a dull day, I did not open that end of the propagator (there are three lids) and on Monday I found I had the problem.

Luckily, I sowed three cells of the tray with these seeds and the separate segments help slow the spread so today I transplanted what I needed from the furthest end of the tray. Copper fungicides, including Cheshunt compound can be used to control the disease once it strikes but it is best to try to avoid the problem with good cultivation.

But there have been some successes:


One of the new plants I am growing this year is Tinantia erecta*. This is a pink-flowered annual related to tradescantia. I have grown Tinantia pringlei and I am very fond of it. The spreading stems have irregular purple spots on the leaves and it blooms for months with its mauve-pink, three-petalled flowers. It is subtle and slightly weedy but I like it. This one though is a robust, fleshy plant with ‘just about noticeable’ slightly nodding, pink flowers that are at their best in the morning – meaning that the petals drop off at noon. The plant looks for all the world like a succulent tricyrtis with sparsely branched, apple green stems and leaves and terminal clusters of blooms. Anyway, the seedlings came up in a few day and two weeks from sowing they look great. As you can see, these are monocotyledons – they have one seed leaf, unlike most seedlings which are dicotyledons and have two seed leaves.

salvia evolution

Although most of my seeds will be sown next month, I get sowing this early partly to stagger the sowings and subsequent pricking out (transplanting) so there is room in the propagator but also because some plants take a long time to bloom so benefit from an early start. These include salvias and my Salvia farinacea ‘Evolution’ are racing along and are now ready for pricking out.

lettuce susan

Although the propagator is set at 20c, which is a good average for most seeds, one end has not bottom heat and only benefits from the heat of the other end so is cooler. It is important not to give your seedlings too much heat so they ‘stretch’ and get leggy. Not only will this encourage damping off but long, stretched seedlings are a nightmare to transplant. So I sowed lettuce and cabbage and calabrese in a tray. All need cooler temperatures than some other plants so once they germinated they were moved to a cool part of the greenhouse to ‘hold’ the seedlings so they became sturdy and tough. But now, before the first true leaves appear between the two cotyledons, they are ready to prick out.

cabbage sedlings

Logically I should say a few words about sowing and pricking out next. So I will do that in a few days.


* I got my seeds from Chiltern Seeds


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One Comment on “Seedlings: success and failure”

  1. joy
    February 18, 2015 at 7:54 am #

    so spring is just around the corner …. I will start very soon

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